linux-kernel - Re: [v6, 5/5] mmc: sdhci-of-esdhc: fix host version for T4240-R1.0-R2.0

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Date:	Thu, 17 Mar 2016 18:06:09 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Rob Herring <robh@...nel.org>
Cc:	Scott Wood <scott.wood@....com>, Yangbo Lu <yangbo.lu@....com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
	Zhao Qiang <qiang.zhao@...escale.com>,
	Russell King <linux@....linux.org.uk>,
	Bhupesh Sharma <bhupesh.sharma@...escale.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Joerg Roedel <joro@...tes.org>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yang-Leo Li <leoyang.li@....com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	Claudiu Manoil <claudiu.manoil@...escale.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Xiaobo Xie <xiaobo.xie@....com>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [v6, 5/5] mmc: sdhci-of-esdhc: fix host version for T4240-R1.0-R2.0

On Thursday 17 March 2016 12:01:01 Rob Herring wrote:
> On Mon, Mar 14, 2016 at 05:45:43PM +0000, Scott Wood wrote:

> > >> This makes the driver non-portable. Better identify the specific
> > >> workarounds based on the compatible string for this device, or add a
> > >> boolean DT property for the quirk.
> > >>
> > >>    Arnd
> > > 
> > > [Lu Yangbo-B47093] Hi Arnd, we did have a discussion about using DTS in v1 before.
> > > https://patchwork.kernel.org/patch/6834221/
> > > 
> > > We don’t have a separate DTS file for each revision of an SOC and if we did, we'd constantly have people using the wrong one.
> > > In addition, the device tree is stable ABI and errata are often discovered after device tree are deployed.
> > > See the link for details.
> > > 
> > > So we decide to read SVR from the device-config/guts MMIO block other than using DTS.
> > > Thanks.
> > 
> > Also note that this driver is already only for fsl-specific hardware,
> > and it will still work even if fsl_guts doesn't find anything to bind to
> > -- it just wouldn't be able to detect errata based on SVR in that case.
> 
> IIRC, it is the same IP block as i.MX and Arnd's point is this won't 
> even compile on !PPC. It is things like this that prevent sharing the 
> driver.

I think the first four patches take care of building for ARM,
but the problem remains if you want to enable COMPILE_TEST as
we need for certain automated checking.

> Dealing with Si revs is a common problem. We should have a 
> common solution. There is soc_device for this purpose.

Exactly. The last time this came up, I think we agreed to implement a
helper using glob_match() on the soc_device strings. Unfortunately
this hasn't happened then, but I'd still prefer that over yet another
vendor-specific way of dealing with the generic issue.

	Arnd